1. The Field of the Invention
The present invention relates to the field of secure digital communications. In particular, the present invention relates to methods and systems for automatically generating a security key, such as an encryption key, using a seed that has random bit sequences.
2. Background and Related Art
Computer networks have transformed the way people communicate and do business. Currently, even sensitive communications traverse public networks, such networks including the Internet. Encryption allows such sensitive communication to be transmitted across public networks with a significantly reduced risk that the messages will be intercepted and decrypted by an unauthorized individual.
Encryption involves the use of an encryption key to manipulate data that is generally readable (also called herein “plain text”) into data that is generally not readable (also called herein “cipher text”). The cipher text may then be transmitted over a public network that is subject to eavesdropping by unauthorized individuals. The authorized recipient uses a decryption key to decrypt the cipher text back into the plain text so that the data may be properly interpreted. Since the general public ideally does not have access to the decryption key, unauthorized users cannot decipher the cipher text and thus cannot interpret the data.
In symmetric encryption, the encryption key and the decryption key are the same. This previously negotiated secret key is ideally only known to authorized participants in a secure communication. However, given sufficient time, knowledge and processing resources, it is possible for unauthorized eavesdroppers to identify the key and thus decrypt any messages they are able to intercept between the authorized participants to the communication.
To guard against this undesirable interception of secure communications, security protocols such as the Wireless Transport Layer Security (WTLS) protocol have provisions for changing the key on a periodic basis. Thus, even if an eavesdropper manages to identify the key, the eavesdropper will only have access to the secure communications until the key is changed.
In these security protocols, a bit sequence called a “master secret” is securely negotiated between two parties to a secure communications session. The master secret is input, along with a bit sequence called a seed, into a one-way hash algorithm to generate an encryption/decryption key. Since the result of the one-way hash algorithm depends on the input seed, changing the seed on occasion also changes the key on occasion. The seed is transmitted in the clear inside a data packet. The recipient uses the seed and the previously negotiated master secret as inputs to the same one-way hash algorithm to generate the same key that was used to encrypt the packet. Since symmetric encryption is employed, that key is then used to decrypt the packet.
In conventional security protocols, such as WTLS, the seed is essentially a bit sequence that is unique to the client. When the seed is to change, the bit sequence is simply incremented. An eavesdropper may take advantage of the predictable changes in the seed to determine the master secret necessary to form the key needed to eavesdrop. It would represent an improvement in the art to provide an encryption/decryption method and system in which the master secret and key is more difficult for an eavesdropper to identify. It would represent yet a further improvement to reduce the damage caused by an eavesdropper if the eavesdropper were to identify the key despite the difficulty in identifying the key.